Metal alloys from molecular inks

ABSTRACT

Low temperature processes for converting mixtures of metal inks into alloys. The alloys can be dealloyed by etching. A method comprising: depositing at least one precursor composition on at least one substrate to form at least one deposited structure, wherein the precursor composition comprises at least two metal complexes, including at least one first metal complex comprising at least one first metal and at least one second metal complex different from the first metal complex and comprising at least one second metal different from the first metal, treating the deposited structure so that the first metal and the second metal become elemental forms of the first metal and the second metal in a treated structure. Further, one can remove at least some of the first metal to leave a nanoporous material comprising at least the second metal. Precursor compositions can be formulated to be homogeneous compositions.

RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 15/923,686, now U.S. Pat No. 10,738,211, which is acontinuation application of U.S. patent application Ser. No. 15/160,018,now U.S. Pat. No. 9,920,212, which is a divisional application of U.S.patent application Ser. No. 13/464,605, now U.S. Pat. No. 9,487,669,which claims priority to U.S. Provisional Application Ser. No.61/482,571, filed May 4, 2011, all of which are incorporated herein byreference in their entirety.

BACKGROUND

Printed electronics is projected to be a multi-billion dollar businesswithin the next 7-10 years, with the inks alone constituting 10-15% ofthat amount, according to some sources. More particularly, a need existsfor better methods of printing metals such as, for example, copper,silver, and gold. These metals are important chip components rangingfrom interconnects to organic field effect transistor source and drainelectrodes. In general, improved compositions and methods for producingmetal structures are needed, particularly for commercial applicationsand inkjet printing. See, for example, U.S. Pat. Nos. 7,270,694;7,443,027; 7,491,646; 7,494,608 (assignee: Xerox); US Patent Publication2010/0163810 (“Metal Inks”); US Patent Publication 2008/0305268 (“LowTemperature Thermal Conductive Inks”); and US Patent Publication2006/0130700 (“Silver Containing Inkjet Inks”).

Metal alloys are important to many areas of technology. However,printing mixtures of metals to form alloys can be difficult to achieve,especially from nanoparticles, as inhomogeneities can arise. Many alloysare prepared using high temperature processing and melting of themetals. A need exists for better, lower temperature methods and inkformulations for use in making alloys.

Furthermore, a need exists for better methods for preparing nanoporousmetallic structures including thin films. See, for example, U.S. Pat.No. 6,805,972 (Erlebacher). Such materials can be used for applicationsranging from, for example, heterogeneous catalysis to biologicaldetection.

Other references are U.S. Patent Publication 2008/294,802; and U.S. Pat.Nos. 7,893,006; 6,491,803; and 7,608,203.

SUMMARY

Provided herein are embodiments for compositions, devices, methods ofmaking compositions and devices, and methods of using compositions anddevices, among other embodiments.

For example, one embodiment provides a method comprising: depositing atleast one precursor composition on at least one substrate to form atleast one deposited structure, wherein the precursor compositioncomprises at least two metal complexes, including at least one firstmetal complex comprising at least one first metal and at least onesecond metal complex different from the first metal complex andcomprising at least one second metal different from the first metal;treating the deposited structure so that the first metal and the secondmetal form elemental forms of the first metal and the second metal in atreated structure.

In one embodiment, the precursor composition is a homogeneouscomposition.

In one embodiment, the precursor composition is prepared by mixing atleast one first metal complex and at least one second metal complex.

In one embodiment, the precursor composition is substantially free ofmetallic nanoparticles. In one embodiment, the precursor composition isfree of metallic nanoparticles. In one embodiment, the precursorcomposition comprises metallic nanoparticles at a level of less than 0.1wt. %.

In one embodiment, the first metal complex is a silver, gold, copper,platinum, iridium, or a rhodium complex. In one embodiment, the firstmetal complex is a silver complex. In one embodiment, the second metalcomplex is a silver, gold, copper, nickel, platinum, iridium, or arhodium complex. In one embodiment, the second metal complex is a goldcomplex. In one embodiment, the precursor composition further comprisesat least one third metal complex different from the first and secondmetal complexes and comprising at least one third metal different fromthe first and second metals. In one embodiment, for the precursorcomposition the atomic percent of the first metal is about 10% to about90% and the atomic percent of the second metal is about 10% to about 90%relative to the total metal content. In one embodiment, moreparticularly, for the precursor composition the atomic percent of thefirst metal is about 20% to about 80% and the atomic percent of thesecond metal is about 20% to about 80% relative to the total metalcontent.

In one embodiment, both the first and the second metal are FCC metals.In another embodiment, both the first and the second metals are BCCmetals.

In one embodiment, the precursor composition further comprises at leastone solvent. In one embodiment, the precursor composition furthercomprises at least one solvent, wherein the solvent is a hydrocarbon.The hydrocarbon can be, for example, linear, branched, or aromatic.

In one embodiment, the amount of the first complex and the secondcomplex relative to the total amount of precursor composition is about500 mg/mL or less. In one embodiment, the amount of the first complexand the second complex relative to the total amount of precursorcomposition is about 250 mg/mL or less.

In one embodiment, the precursor composition has a viscosity adapted foruse in ink jet printing for the depositing step. In one embodiment, forexample, the precursor composition has a viscosity of about 100 cps orless at 25° C.

In one embodiment, the first metal complex and the second metal complexeach comprise only one metal center. In one embodiment, the first metalof the first metal complex and the second metal of the second metalcomplex each are in an oxidation state of (I) or (II). In oneembodiment, the first metal complex and the second metal complex areeach neutral complexes. In one embodiment, the first metal complexcomprises at least one carboxylate ligand. In one embodiment, the firstmetal complex comprises at least one multidentate amino ligand. Theligand can be, for example, unsymmetrical. In one embodiment, the firstmetal complex comprises at least one carboxylate ligand and at least onemultidentate amino ligand. In one embodiment, the second metal complexcomprises at least one carboxylate ligand. In one embodiment, the secondmetal complex comprises at least one sulfur-containing ligand. In oneembodiment, the second metal complex comprises at least one carboxylateligand and at least one sulfur-containing ligand, such as a thioether.In one embodiment, the depositing step comprises drop casting, spincoating, ink jet printing, roll-to-roll, slot-die, gravure, microcontactprinting, or flexographic printing. In one embodiment, the depositingstep comprises ink jet printing. In one embodiment, the depositing stepis not carried out under a vacuum. In one embodiment, the depositingstep does not comprise sputtering. In one embodiment, the depositingstep does not comprise electrochemical deposition.

In one embodiment, the depositing step is carried out at least twice onthe same position on the substrate. In one embodiment, the depositedstructure is a line. In one embodiment, the substrate is flexible orrigid. In one embodiment, the substrate is a polymeric substrate. In oneembodiment, the substrate is glass or a semiconductor material. In oneembodiment, the treating step is a heating step or an exposure toradiation step. In one embodiment, the treated structure has a thicknessof about 500 nm or less. In one embodiment, the treating step is aheating step at less than 250° C. In one embodiment, the treating stepis a heating step at less than 200° C.

In one embodiment, the two elemental metals in the treated structure arein the form of an alloy. In one embodiment, the two elemental metals inthe treated structure are in the form of a solid solution. In oneembodiment, the two elemental metals in the treated structure are not inthe form of a solid solution. In one embodiment, the atomic ratio ofmetals in the precursor composition and in the treated deposit issubstantially the same. In one embodiment, the atomic ratio of metals inthe precursor composition and in the treated deposit are within fivepercent of each other. In one embodiment, the atomic ratio of metals inthe precursor composition and in the treated deposit are within onepercent of each other.

In one embodiment, one can further remove at least some of the firstmetal to leave a nanoporous material comprising at least the secondmetal. In one embodiment, the removing step is chemical removal byselective etching. In one embodiment, the removing is not anelectrochemical removal. In one embodiment, the removing is carried outwith acid. In one embodiment, the nanoporous material has an averagepore size of about 100 nm or less. In one embodiment, at least a portionof the first metal which is removed is recovered. In one embodiment, thenanoporous material is further subjected to a chemisorption step. In oneembodiment, the nanoporous material is further chemically orbiochemically modified. In one embodiment, the nanoporous material isfurther used in a metal Plasmon frequency monitoring process. In oneembodiment, the first and second metals are silver, gold, copper,platinum, iridium, nickel, or rhodium, and the precursor compositionfurther comprises at least one solvent. In one embodiment, the first andsecond metals are silver or gold, and the precursor composition furthercomprises at least one hydrocarbon solvent.

In one embodiment, the first and second metals are silver or gold, andthe precursor composition further comprises at least one hydrocarbonsolvent, the depositing step comprises ink jet printing, and thetreating step is a heating step at a temperature of less than 250° C.,and a removing step is carried out by chemical etching.

Another embodiment provides a composition comprising: at least one firstmetal complex, wherein the first metal complex comprises a first metaland at least one first ligand and at least one second ligand, differentfrom the first ligand, for the first metal; at least one second metalcomplex, which is different from the first metal complex, and comprisesa second metal and at least one first ligand and at least one secondligand, different from the first ligand, for the second metal; at leastone solvent, wherein (i) the selection of the amount of the first metalcomplex and the amount of the second metal complex, (ii) the selectionof the first ligands and the selection of the second ligands for thefirst and second metals, and (iii) the selection of the solvent areadapted to provide a homogeneous composition.

Another embodiment provides a composition comprising: at least one firstmetal complex, wherein the first metal complex is a neutral,dissymetrical complex comprising at least one first metal in anoxidation state of (I) or (II), and at least two ligands, wherein atleast one first ligand is an amine and at least one second ligand is acarboxylate anion; at least one second metal complex, which is differentfrom the first metal complex, wherein the second metal complex is aneutral, dissymmetrical complex comprising at least one second metal inan oxidation state of (I) or (II), and at least two ligands, wherein atleast one first ligand is sulfur compound and at least one second ligandis the carboxylate anion of the first metal complex; at least oneorganic solvent, and wherein the atomic percent of the first metal isabout 20% to about 80% and the atomic percent of the second metal isabout 20% to about 80% relative to the total metal content.

Another embodiment provides a method comprising: combining at least onefirst precursor composition comprising at least one first metal complexand at least one first solvent, and at least one second precursorcomposition comprising at least one second metal complex different fromthe first and at least one second solvent, wherein the amounts of thefirst and second precursor compositions, the first and second solvent,and the ligands of the first and second metal complexes are selected toform a homogeneous and/or completely miscible composition.

At least one additional advantage in at least one embodiment includesformation of porous metal networks that display high conductivity andflexibility.

At least one additional advantage in at least one embodiment includeshigh optical transparency including increased transparency upon etching.

At least one additional advantage in at least one embodiment includesability to form homogeneous inks which allow for an intimate alloy to beformed.

At least one additional advantage in at least one embodiment includesease of controlling film stoichiometry.

At least one additional advantage in at least one embodiment includesability to tune physical properties of the end product, such as, forexample, work function, adhesion, and the like. For example, adhesion tothe underlying substrate can be better controlled in at least oneembodiment.

At least one advantage in at least one embodiment includes lowtemperature processing.

At least one additional advantage in at least one embodiment includesnot using expensive and cumbersome vacuum conditions and equipment forprocessing.

At least one additional advantage in at least one embodiment includesability to tune and control closely the atomic ratio of the metals inthe alloy. This can allow, for example, tuning of work function. Thatcan be important for, for example, lowering the overpotential for chargeinjection into organic semiconductive devices.

At least one additional advantage in at least one embodiment includeslowering of cost by using a less expensive metal as a filler componentin an alloy.

At least one additional advantage in at least one embodiment includesproviding an excellent, high surface area, porous medium for detectionof various analytes. For example, metal Plasmon frequency monitoring canbe carried out.

At least one additional advantage in at least one embodiment includesability to recycle metal which has been removed.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates embodiments, showing line printing by ink jetprinting at different atomic ratios of silver-gold ink after depositionand metallization (including a one time deposition (1×) and a two timedeposition (2×).

FIG. 2 illustrates one embodiment, showing SEM/EDX of the resultingalloy from an ink containing a 60% Ag and 40% Au atomic ratio (lowermagnification).

FIG. 3 illustrates one embodiment, showing SEM/EDX of the resultingalloy from an ink containing a 60% Ag and 40% Au atomic ratio (highermagnification compared to FIG. 2).

FIG. 4 illustrates one embodiment, showing SEM/EDX of the resultingalloy from an ink containing a 20% Ag and 80% Au atomic ratio.

FIGS. 5A, 5B, and 5C illustrate one embodiment, showing structuralcharacterization of Ag film (5A), gold film (5B), and electrum metallicalloy films by PXRD (Au:Ag=50:50).

FIGS. 6A and 6B illustrate one embodiment, showing diffraction overlaysof Au, Ag and the resulting alloy (Au:Ag=50:50). FIG. 6A shows a broaderrange than FIG. 6B.

Figures include, in some cases, color figures and features, and thecolor features form part of the disclosure.

DETAILED DESCRIPTION Introduction

Priority provisional U.S. Ser. No. 61/482,571 filed May 4, 2011 isincorporated herein by reference in its entirety.

U.S. Ser. No. 12/941,932 (assignee: Carnegie Mellon University; “MetalInk Compositions, Conductive Patterns, Methods, and Devices”) filed Nov.8, 2010 and U.S. Ser. No. 61/603,852 (“Self-Reducing Metal Complex InksSoluble In Polar Protic Solvents”) are hereby incorporated by referencefor all purposes in their entireties. This includes the description ofthe precursor compositions, metal complexes, deposition, conversion tometals, the figures, the working examples, and the claims.

In addition, the PhD thesis by Anna Javier submitted to Carnegie MellonUniversity, dated Apr. 26, 2010 and entitled “Solution-ProcessableMaterials for Printed Electronics,” is also incorporated by reference,including Chapter 5 entitled “Solution-Processable Metal-OrganicComplexes for Printable Metals.”

Microfabrication, printing, ink jet printing, electrodes, andelectronics are described in, for example, Madou, Fundamentals ofMicrofabrication, The Science of Miniaturization, 2nd Ed., 2002.

Organic chemistry methods and structures are described in, for example,March's Advanced Organic Chemistry, 6th Ed., 2007.

Metals, metal alloys, and metal solid solutions are known in the art.See, for example, Shackelford, Introduction to Materials Science forEngineers, 4th Ed., 1996; Metals Handbook, 9th Ed., Vol. 2, AmericanSociety for Metals, Metals Park, Ohio, 1979. Examples include ferrousalloys, including carbon and low-alloy steels, high-alloy steels, castirons, and rapidly solidified ferrous alloys. Other examples arenonferrous alloys including aluminum, magnesium, titanium, copper,nickel, zinc, lead, and other alloys.

Inks and alloys are noted in, for example, Ginley U.S. PatentPublication 2010/0163810; Kodas U.S. Pat. No. 6,951,666; Li U.S. Pat.No. 7,270,694; Kodas U.S. Pat. No. 7,553,512; and Castillo U.S. PatentPublication No. 2009/0188556.

One embodiment described in further detail below provides a methodcomprising: depositing at least one precursor composition on at leastone substrate to form at least one deposited structure, wherein theprecursor composition comprises at least two metal complexes, includingat least one first metal complex comprising at least one first metal andat least one second metal complex different from the first metal complexand comprising at least one second metal different from the first metal,treating the deposited structure so that the first metal and the secondmetal form elemental forms of the first metal and the second metal in atreated structure. Optionally, one can remove at least some of the firstmetal to leave a nanoporous material comprising at least the secondmetal.

Precursor composition

The precursor composition, which can be also called an ink, is adaptedto be deposited onto a substrate. The precursor composition can beliquid at ambient temperature. Moreover, after deposition, it can betreated to form elemental metal structures. Here, the metal is, forexample, reduced from a (I) or (II) valent state to a zero valent,elemental state, forming the base metal in a mixture with at least oneother base metal in an elemental, zero valent state.

The precursor composition can comprise at least one first metal complex,and at least one second metal complex different from the first. It canoptionally comprise a third metal complex, or a fourth metal complex,and so forth, with additional metal complexes, wherein each of the metalcomplexes are different from the other complexes.

In one embodiment, the first and second metal complexes do not reactwith each other when they are mixed together in the precursorcomposition.

The precursor composition can further comprise at least one solventincluding a linear, branched, or aromatic hydrocarbon solvent such astoluene. In another embodiment, the solvent is a polar protic solvent,such as water, alcohol (including methanol, ethanol, propanol, and thelike), glycol, amine or PEG (including ethylene glycol and propyleneglycol). In a further embodiment, the solvent system comprises a mixtureof solvents. Optionally, the precursor composition can compriseadditives including, for example, surfactants, dispersants, binders, andviscosity modifiers.

The metal complexes can be self-reducing.

The precursor composition can be a homogeneous composition.

The precursor composition can be a composition that does not phaseseparate upon mixing.

One can examine the compositions with an unaided eye under ambientconditions for homogeneity and phase separation. In addition, one canmeasure homogeneity and phase separation by visual inspection with theunaided eye, as well as with instrumental methods like opticalmicroscopy and/or light scattering.

In addition, the primary focus is to use molecular compounds rather thannanoparticles to achieve the desired results. Hence, the precursorcomposition can be substantially free or totally free of metallicnanoparticles. In one embodiment, the precursor composition comprisesmetallic nanoparticles at a level of less than 0.1 wt. %, or less than0.01 wt. %, or less than 0.001 wt. %. One can examine compositions forparticles using methods known in the art including, for example, SEM andTEM, spectroscopy including UV-Vis, plasmon resonance, and the like.Nanoparticles can have diameters of, for example, 1 nm to 500 nm, or 1nm to 100 nm. The composition comprising the metal complexes can be alsofree of flakes.

In one embodiment, the precursor composition does not comprise apolymer. In one embodiment, the precursor composition does not comprisea surfactant. In one embodiment, the composition comprises only metalcomplexes and solvent.

In one embodiment, the precursor composition further comprises at leastone solvent. The solvent can be, for example, a hydrocarbon including anaromatic hydrocarbon. The solvent can be, for example, a polar proticsolvent, such as water, alcohol, glycol, amine or PEG. Alcohols includemethanol, ethanol, propanol, and the like.

In one embodiment, the metal complexes are used without additionalsolvent.

In one embodiment, the composition is free of, or substantially free ofwater. For example, the amount of water can be less than 1 wt. %, or theamount of water can be less than 0.1 wt. %, or less than 0.01 wt. %.

In one embodiment, the composition is free of, or substantially free ofoxygenated solvent. For example, the amount of oxygenated solvent can beless than 1 wt. %. Or, the amount of oxygenated solvent can be less than0.1 wt. %, or less than 0.01 wt. %. Oxygenated solvents include, forexample, water, methanol, ethanol, alcohols including primary,secondary, and tertiary alcohols, glycols including ethylene glycol,polyethers, aldehydes, and the like.

In one embodiment, the precursor composition has a viscosity adapted foruse in ink jet printing for the depositing step. In general, theviscosity can be adapted for the deposition method.

In one embodiment, the viscosity measured at 25° C. can be, for example,about 500 cps or less, or about 250 cps or less, or about 100 cps orless. In another embodiment, it can be about 1,000 cps or more. In oneembodiment, the precursor composition has a viscosity of about 1 cps toabout 20 cps, or about 1 cps to about 10 cps.

Metal Complexes

The metal complex, including first and second metal complexes, can be aprecursor to a homogeneous mixture of two or more complexes that is aprecursor to a metal alloy film. Metal organic and transition metalcompounds, metal complexes, metals, and ligands are described in, forexample, Lukehart, Fundamental Transition Metal Organometllic Chemistry,Brooks/Cole, 1985; Cotton and Wilkinson, Advanced Inorganic Chemistry: AComprehensive Text, 4th Ed., John Wiley, 2000.

In one embodiment of the metal complexes of this invention are describedin U.S. Ser. No. 12/941,932 and U.S. Ser. No. 61/603,852, including theworking examples. The metal complex can be homoleptic or heteroleptic.The metal complex can be mononuclear, dinuclear, trinuclear, and higher.The metal complex can be a covalent complex. The metal complex can befree from metal-carbon formal bonding. The metal complexes can bereadily soluble at 25° C.

The first metal complex can comprise at least one first metal, and thesecond metal complex can comprise at least one second metal, and thethird metal complex can comprise at least on third metal, and so forth.

The metal complexes can be soluble, including soluble in, for example, anon-polar or less polar solvent such as a hydrocarbon, including anaromatic hydrocarbon. Aromatic hydrocarbon solvents to test solubilityinclude, for example, benzene and toluene, as well as xylene andmixtures of xylenes. Polyalkylaromatics can be used. Further, the metalcomplexes can be soluble in, for example, a polar protic solvent such aswater, alcohol, glycol, amine or PEG.

The metal complexes can be dissymmetric which can facilitate solubilityand good homogeneity for mixtures of metal complexes. Dissymmetricmolecules are known in the art. See, for example. Cotton, ChemicalApplications of Group Theory, 3rd Ed., and U.S. Pat. Nos. 7,001,526,5,585,457, 4,619,970, and 4,410,538. Dissymmetric molecules can have aC1 symmetry with only the identity operator E.

Metals and transition metals are known in the art. Examples include Sc,Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag,Cd, La, Hf, Ta, W, Re, Os, Ir, Pt, Au, and Hg. In particular, coinagemetals can be used including silver, gold, and copper. Precious metalscan be used including gold, iridium, osmium, palladium, platinum,rhodium, ruthenium, and silver. In other preferred embodiments,platinum, nickel, cobalt, and palladium can be used. Still further,lead, iron, tin, ruthenium, rhodium, iridium, zinc, and aluminum can beused. Other metals and elements can be used as known in the art.

In one embodiment, the first metal complex is a silver, gold, copper,platinum, nickel, iridium, or rhodium complex. In one embodiment, thefirst metal complex is a silver complex.

In one embodiment, the second metal complex is a silver, gold, copper,platinum, nickel, iridium, or rhodium complex. In one embodiment, thesecond metal complex is a gold complex.

In one embodiment, the precursor composition further comprises at leastone third metal complex different from the first and second metalcomplexes and comprising at least one third metal different from thefirst and second metals. The third metal can be, for example, copper,platinum, and iridium. In one embodiment, in particular, the third metalis copper.

In one embodiment, for the precursor composition the atomic percent ofthe first metal is about 1% to about 99% and the atomic percent of thesecond metal is about 1% to about 99% relative to the total metalcontent. In one embodiment, for the precursor composition the atomicpercent of the first metal is about 10% to about 90% and the atomicpercent of the second metal is about 10% to about 90% relative to thetotal metal content. In another embodiment, for the precursorcomposition, the atomic percent of the first metal is about 20% to about80% and the atomic percent of the second metal is about 20% to about 80%relative to the total metal content.

The total amount of metal complex, including for example the totalamount of the first metal complex and the second metal complex, relativeto the total amount of precursor composition is about 500 mg/mL or less,or about 250 mg/mL or less, or about 200 mg/mL or less, or about 150mg/mL or less, or about 100 mg/mL or less. The lower amount can be, forexample about 1 mg/mL or more, or about 10 mg/mL or more. Ranges can beformulated with these upper and lower embodiments, including forexample, about 1 mg/mL to about 500 mg/mL. One particular range is about60 mg/mL to about 200 mg/mL.

In one embodiment, the first metal complex and the second metal complexeach comprise only one metal center.

In one embodiment, the first metal of the first metal complex and thesecond metal of the second metal complex each are in an oxidation stateof (I) or (II).

The metal complex can comprise a plurality of ligands including two ormore ligands, or just two ligands. There can be, for example, a firstligand and a second ligand, different from each other. The first ligandcan provide sigma electron donation, or dative bonding. The first ligandcan be in a neutral state, not an anion or cation. Examples of the firstligand include amines, oxygen-containing ligands, and sulfur-containingligands including oxygenated ethers and thioethers, including cyclicthioethers. Asymmetrical or symmetrical amines can be used. The aminescan comprise, for example, at least two primary or secondary aminegroups. Monodentate ligands can be used. Polydentate or multidentateligands can be used. Alkylamino ligands can be used.

The second ligand can be different from the first ligand and canvolatilize upon heating the metal complex. For example, it can releasecarbon dioxide, as well as volatile small organic molecules such aspropene, in some embodiments. The second ligand can be a chelator withminimum number of atoms that can bear an anionic charge and provide aneutral complex. The second ligand can be anionic. For example, thesecond ligand can be a carboxylate, including a carboxylate comprising asmall alkyl group. The number of carbon atoms in the alkyl group can be,for example, ten or less, or eight or less, or five or less. Themolecular weight of the second ligand can be, for example, about 1,000g/mol or less, or about 250 g/mol or less, or about 150 g/mole or less.

The first and second ligand, as well as any other ligands, can beselected to provide dissymmetrical complexes.

In one embodiment, the first metal complex comprises at least onecarboxylate ligand. In one embodiment, the first metal complex comprisesat least one amino ligand. In one embodiment, the first metal complexcomprises at least one carboxylate ligand and at least one amino ligand.

In one embodiment, the second metal complex comprises at least onecarboxylate ligand. In one embodiment, the second metal complexcomprises at least one neutral, sulfur-containing ligand. In oneembodiment, the second metal complex comprises at least one carboxylateligand and at least one neutral, sulfur-containing ligand.

Specific examples of metal complexes include:

As described more below, the complexes can be treated to form elementalmetal alloys. If desired, one or more of the metals in the alloy can beremoved.

Examples of binary combinations of metals to form binary alloys includeAg—Au, Pt—Rh, Au—Cu, Zn—Cu, Pt—Cu, Ni—Al, Cu—Al, Pt—Ni, and Pt—Ir.

One of the metals can be removed if desired, and the selection of thefirst metal and the second metal can be adapted so that one (the firstmetal) can be removed. For example, aluminum can be removed as a firstmetal from a nickel-aluminum alloy to yield porous nickel, or from acopper-aluminum alloy to yield porous copper. If a third metal oradditional metal is present, it can be adapted to be removed or toremain upon removal of metal.

Examples of ternary metal combinations and alloys include, for example,Fe—Ni—Cr, Co—Cr—Fe, Co—Cr—Ni, Co—Cr—W, Co—Fe—Mo, Co—Fe—Ni, Co—Fe—W, andCo—Mo—Ni.

Quaternary metal combinations and alloys are known in the art and can beprepared.

Combinatorial arrays of alloys can be prepared. The concentrations ofthe metal in the alloy can be varied, and it can be controlled by theconcentration of the metal (or metal complex) in the precursorcomposition. Gradient embodiments can be practiced where, for example,multilayer structures can be prepared with varying, gradientconcentrations of metal from layer to layer. Upon heating, the metalswill begin to diffuse giving rise to a functionally graded alloy ofmetals varied from their interfaces.

Selections for Homogeneous Precursor Compositions

One embodiment provides a composition comprising: at least one firstmetal complex, wherein the first metal complex comprises a first metaland at least one first ligand and at least one second ligand, differentfrom the first ligand, for the first metal; at least one second metalcomplex, which is different from the first metal complex, and comprisesa second metal and at least one first ligand and at least one secondligand, different from the first ligand, for the second metal; at leastone solvent, wherein (i) the selection of the amount of the first metalcomplex and the amount of the second metal complex, (ii) the selectionof the first ligands and the selection of the second ligands for thefirst and second metals, and (iii) the selection of the solvent areadapted to provide a homogeneous composition.

In one embodiment, for example, the first metal complex is a silver,gold, copper, platinum, iridium, nickel, or rhodium complex. Inparticular, the first metal complex can be a silver complex.

In one embodiment, the second metal complex is a silver, gold, copper,platinum, iridium, nickel, or rhodium complex. In a particularembodiment, the second metal complex is a gold complex.

In additional embodiments, the first metal complex is a silver complexand the second metal complex is a gold complex, or the first metalcomplex is a platinum complex and the second metal complex is a goldcomplex, or the first metal complex is a platinum complex and the secondmetal complex is an iridium complex, or the first metal complex is aplatinum complex and the second metal complex is a rhodium complex. Forexample, in one embodiment, the first metal complex is a silver complexand the second metal complex is a gold complex.

In one embodiment, the first ligand of the first metal complex is acarboxylate. In another embodiment, the first ligand of the second metalcomplex is a carboxylate. In one embodiment, the two first ligands ofthe two complexes are the same.

In one embodiment, the first metal complex and the second metal complexare each dissymmetric complexes.

In one embodiment, the atomic percent of the first metal is about 10% toabout 90% and the atomic percent of the second metal is about 10% toabout 90% relative to the total metal content. In another embodiment,the atomic percent of the first metal is about 20% to about 80% and theatomic percent of the second metal is about 20% to about 80% relative tothe total metal content.

In one embodiment, the solvent is a hydrocarbon, or an aromatichydrocarbon, or a substituted aromatic hydrocarbon. In anotherembodiment, the solvent is a polar protic solvent such as water,alcohol, glycol, amine or PEG.

In one embodiment, the first and second metal complexes comprise atleast 25 wt. % metal, or at least 50 wt. % metal, or at least 70 wt. %metal.

In one embodiment, the amount of the first complex and the secondcomplex relative to the total amount of composition is about 500 mg/mLor less, or about 250 mg/mL or less.

In one embodiment, the composition has a viscosity adapted for use inink jet printing. For example, the precursor composition can have aviscosity of about 1 cps to about 20 cps.

In one embodiment, the first metal complex and the second metal complexeach comprise only one metal center.

In another embodiment, the first metal of the first metal complex andthe second metal of the second metal complex each are in an oxidationstate of (I) or (II).

In one embodiment, the first metal complex comprises at least onealkylcarboxylate ligand. In one embodiment, the first metal complexcomprises at least one amino ligand. In one embodiment, the first metalcomplex comprises at least one carboxylate ligand and at least one aminoligand.

In another embodiment, the second metal complex comprises at least onealkylcarboxylate ligand. In addition, the second metal complex cancomprise at least one sulfur-containing ligand. In addition, the secondmetal complex can comprise at least one carboxylate ligand and at leastone sulfur-containing ligand.

In one embodiment, the first metal complex is a silver complex, and thesecond metal complex is a gold complex.

In one embodiment, the precursor composition is totally free of metallicnanoparticles.

In one embodiment, the first metal complex comprises at least onecarboxylate ligand and at least one amine ligand, and the second metalcomplex comprises at least one carboxylate ligand and at least onethioether ligand. The amine ligand can be polydentate.

In one embodiment, the first metal complex and the second metal complexeach comprise a carboxylate ligand which is the same for each complex.

In one embodiment, the first metal complex and the second metal complexeach comprise a carboxylate ligand which has eight or fewer carbonatoms.

In one embodiment, the solvent is a hydrocarbon, and wherein the amountof the first complex and the second complex relative to the total amountof composition is about 500 mg/mL or less.

In one embodiment, the first metal complex is a silver complex, and thesecond metal complex is a gold complex, and wherein the amount of thefirst complex and the second complex relative to the total amount ofcomposition is about 500 mg/mL or less.

In one embodiment, the first metal complex is a silver complex, and thesecond metal complex is a gold complex, and wherein the amount of thefirst complex and the second complex relative to the total amount ofcomposition is about 500 mg/mL or less, and wherein the composition hasa viscosity adapted for use in ink jet printing.

In one embodiment, the first metal complex is a silver complex, and thesecond metal complex is a gold complex, wherein the precursorcomposition is substantially free of metallic nanoparticles, and whereinthe first metal of the first metal complex and the second metal of thesecond metal complex each are in an oxidation state of (I) or (II).

In one embodiment, the atomic percent of the first metal is about 20% toabout 80% and the atomic percent of the second metal is about 20% toabout 80% relative to the total metal content, wherein the solvent is ahydrocarbon, and wherein the first and second metal complexes compriseat least 50 wt. % metal.

Another Embodiment for Precursor Composition

In another embodiment, a precursor composition is provided comprising:at least one first metal complex, wherein the first metal complex is aneutral complex comprising at least one first metal in an oxidationstate of (I) or (II), and at least two ligands, wherein at least onefirst ligand is an amine and at least one second ligand is a carboxylateanion; at least one second metal complex, which is different from thefirst metal complex, wherein the second metal complex is a neutralcomplex comprising at least one second metal in an oxidation state of(I) or (II), and at least two ligands, wherein at least one first ligandis sulfur compound and at least one second ligand is the carboxylateanion of the first metal complex; and at least one organic solvent, andwherein the atomic percent of the first metal is about 20% to about 80%and the atomic percent of the second metal is about 20% to about 80%relative to the total metal content.

Methods of Making Metal Complexes and Precursor Compositions

The metal complexes can be made by a variety of methods, many of whichare described in U.S. Ser. No. 12/941,932 and U.S. Ser. No. 61/603,852and incorporated herein by reference. Precursor compositions can be madeby combining the metal complex containing the first metal with the metalcomplex containing the second metal to obtain a mixture. In one example,the solubility or homogeneity the metal complex composition may be tunedby alternating and/or decorating the periphery of the organic ligandsassociated with one or more of the metal complexes.

In one embodiment, the mixture does not show separation upon visualobservation. In one embodiment, the mixture is a homogeneous solution.In one embodiment the mixture contains a solvent.

One embodiment provides a method comprising: combining at least onefirst precursor composition comprising at least one first metal complexand at least one first solvent, and at least one second precursorcomposition comprising at least one second metal complex different fromthe first and at least one second solvent, wherein the amounts of thefirst and second precursor compositions, the first and second solvent,and the ligands of the first and second metal complexes are selected toform a homogeneous composition.

Depositing

Methods known in the art can be used to deposit inks including directand indirect methods. See, for example. Direct-Write Technologies forRapid Prototyping Applications (Ed. A. Pique and D. Chrisey), 2002.Methods for depositing include, for example, spin coating, pipetting,inkjet printing, blade coating, rod coating, dip coating, lithography oroffset printing, gravure, flexography, screen printing, stencilprinting, drop casting, slot die, roll-to-roll, spraying, microcontactprinting, and stamping. One can adapt the ink formulation and thesubstrate with the deposition method. See also Direct Write Technologiesbook cited above, wherein for example, chapter 7 describes inkjetprinting. Contact and non-contact deposition can be used. In oneembodiment, evaporation or vacuum deposition is not used. In oneembodiment, sputtering is not used. The line-of-sight issues, highvacuum and high expenses associated with sputtering can be avoided.Liquid deposition can be used.

In one embodiment, the depositing step comprises drop casting, spincoating, inkjet printing, roll-to-roll, slot-die, gravure, andmicrocontact printing. For spin coating, the rpm can be, for example,500 rpm to 10, 000 rpm, or 700 rpm to 5,000 rpm.

In one embodiment, the depositing step comprises inkjet printing. In oneembodiment, the depositing step is not carried out under a vacuum. Inone embodiment, the depositing step does not comprise sputtering. In oneembodiment, the depositing step does not comprise electrochemicaldeposition.

In one embodiment, the depositing step is carried out at least twice onthe same position on the substrate. The same precursor composition canbe used in the multiple layers, or different precursor compositions canbe used from layer-to-layer.

One can adapt the viscosity of the ink to the deposition method. Forexample, viscosity can be adapted for ink jet printing. Viscosity canbe, for example, about 500 Cps or less. Or viscosity can be, forexample, 1,000 Cps or more.

One can also adapt the concentration of dissolved solids in the ink. Theconcentration of the dissolved solids in the ink can be, for example,about 500 mg/mL or less, or about 250 mg/mL or less, or about 100 mg/mLor less, or about 150 mg/mL or less, or about 100 mg/mL or less. A loweramount can be, for example, about 1 mg/mL or more, or about 10 mg/mL ormore. Ranges can be formulated with these upper and lower embodimentsincluding, for example, about 1 mg/mL to about 500 mg/mL. In addition,the wetting properties of the ink can be adapted.

Additives such as, for example, surfactants, dispersants, and/or binderscan be used to control one or more ink properties if desired for use ina particular depositing method. In one embodiment, an additive is notused. In one embodiment, a surfactant is not used.

Nozzles can be used to deposit the precursor, and nozzle diameter canbe, for example, less than 100 microns, or less than 50 microns. Theabsence of particulates can help with prevention of nozzle clogging.

In deposition, solvent can be removed, and the initial steps forconverting metal precursor to metal can be started.

Multiple deposition steps can be carried out, and multi-layers can beformed.

In one embodiment, the deposited structure can be a film or a line, forexample, whether linear or curvilinear. In another embodiment, thedeposited structure is a dot, spot, circle, or vertex-shared polygon orpolygon-like structures.

Substrate

A wide variety of solid materials can be subjected to deposition of themetal inks. Polymers, plastics, metals, ceramics, glasses, silicon,semiconductors, insulators, and other solids can be used. Organic andinorganic substrates can be used. High temperature polymers can be used.Polyester or polyimide types of substrates can be used. Paper substratescan be used. Printed circuit boards can be used. Substrates used inapplications described herein can be used.

Other examples of substrates include three dimensional substrates,fabrics, gauze, porous substrates, and antimicrobial substratesincluding porous antimicrobial substrates.

Substrates can comprise electrodes and other structures includingconductive or semiconductive structures.

In one embodiment, the substrate is a flexible or a rigid substrate. Inone embodiment, the substrate is a polymeric substrate. In oneembodiment, the substrate is a glass or a semiconductor material.

Treating or Converting Step

The inks and compositions comprising metal complexes can be depositedand treated, reacted, or otherwise converted to metallic structuresincluding films and lines. Heat and/or light can be used including laserlight. A variety of radiations can be used including a full spectrum ofwavelengths. Electron beam, x-ray, and/or deep UV methods can be used.The atmosphere around the metal film can be controlled. For example,oxygen can be included or excluded. Volatile by-products can beeliminated.

The heating temperature can be lower than the melting temperature of themetals.

The heating temperature can be determined with use of measurement of thethermal decomposition profiles.

In one embodiment, the treating step is a heating step or an exposure toradiation step.

In one embodiment, the treating step is a heating step at less than 300°C. In one embodiment, the treating step is a heating step at less than250° C. In one embodiment, the treating step is a heating step at lessthan 200° C. In one embodiment, the treating step is a heating step atless than 150° C.

In one embodiment, the two elemental metals in the treated structure arein the form of an alloy.

In one embodiment, the two elemental metals in the treated structure arein the form of a solid solution. In one embodiment, the two elementalmetals in the treated structure are not in the form of a solid solution.

In one embodiment, the atomic ratio of metals in the precursorcomposition and in the treated deposit is substantially the same. Inanother embodiment, the atomic ratio of metals in the precursorcomposition and in the treated deposit are within ten percent of eachother. In another embodiment, the atomic ratio of metals in theprecursor composition and in the treated deposit are within five percentof each other. In another embodiment, the atomic ratio of metals in theprecursor composition and in the treated deposit are within one percentof each other.

Treated Structure: Metallic Lines after Deposition and Treatment

The metallic structures, including lines and films, can be coherent andcontinuous. Continuous metallization can be observed with goodconnectivity between grains and low surface roughness.

The metals can form an alloy. The metals can form a solid solution. Inone embodiment, electrum-like alloys can be prepared.

Line width can be, for example, 1 micron to 500 microns, or 5 microns to300 microns. Line width can be less than one micron if nanoscalepatterning methods are used.

Line thickness can be, for example, about one micron or less, or about500 nm or less, or about 300 nm or less, or about 100 nm or less.

Dots or circles can be also made. Curvilinear structures can be made. Inaddition, vertex-shared polygon or polygon-like structures, such asvertex-shared polyhedrons, can be made.

In one embodiment, ink formulations can be converted to metallic linesand films without formation of substantial amounts of metal particles,microparticles, or nanoparticles.

Metal lines and films can be prepared with characteristics of metal andlines prepared by other methods like sputtering.

Metal lines and films can be, for example, at least 90 wt. % metal, orat least 95 wt. % metal, or at least 98 wt. % metal.

Metal lines and films can be relative smooth (<10 nm) according to AFMmeasurements.

Metal lines and films can be used to join structures such as electrodesor other conductive structures.

The metal can have a work function which is substantially the same as anative metal work function, or in the case of alloys, work functionsthat reflect the mixture of metals. For example, the difference can be25% or less, or 10% or less.

Lines and grids can be formed. Multi-layer and multi-component metalfeatures can be prepared.

Some alloys such as a gold-silver alloy can provide excellent transportproperties with superior alloy adhesion to a substrate compared to thatof either pure metal alone.

In one embodiment, the metallic structure is different in size comparedto the metal leaf as described in WO 2004/020064 (Erlebacher).

Dealloying, Removal of Metal

The metal complexes and methods of using them can be selected so thatone metal can be separated from the other metal. Dealloying can becarried out by methods such as chemical etching or electrochemicalmethods. Dealloying, for example, is described in WO 2004/020064(Erlebacher). See also U.S. Pat. No. 4,977,038 (Sieradzki).

The dealloying can be carried out when the metallic structure isdisposed on the substrate.

In one embodiment, the removal step is not optional but carried out.

In one embodiment, the removing step is a chemical removal. In oneembodiment, the removing is not an electrochemical removal.

The metallic lines can be, for example, selectively etched to removesome or all of the first metal from the reacted deposit to yield aporous metallic material. Methods for removal of some or all of oneelemental metal from a mixture of two or more elemental metals is knownin the art. For etching, the temperature of etching can be, for example,about 20° C. to about 50° C. Methods like sonication can be carried outto enhance removal.

Etching can be carried out with use of acid, including inorganic ororganic acid. Mineral acids can be used including, for example, nitricacid, sulfuric acid, or hydrochloric acid. Perchloric acid can be used.A single acid or a mixture of acids including, for example, aqua regia,can be used. For etching, if carried out with acid, the concentration ofthe acid can be, for example, 3 M or less, or 1 M or less. In anotherembodiment, thionyl chloride can be used.

In one embodiment, the first metal is selectively removed by contactwith acidic aqueous solution.

The etching/dealloying can cause a change in impedance of the resultingnanoporous material. As a result, the nanoporous material may have aunique electrical property for various biological applications,including, for example, stimulating muscle response in vivo.

In one embodiment, the etching/dealloying results in a gold nanoporousmaterial suitable for making glucose sensors.

Nanoporous material

In one embodiment, the nanoporous material has an average pore size ofabout 100 nm or less, or about 50 nm or less, or about 25 nm or less.Porosity and other properties can be measured by methods known in theart including, for example, SEM and BET. In addition, the nanoporousmaterials can be characterized by nanoindentation methods.

Other processing steps

In one embodiment, at least a portion of the first metal such as silverwhich is removed is recovered. For example, at least 50 wt. %, or atleast 75 wt. %, or at least 90 wt. %, of the material can be recovered.

In one embodiment, the nanoporous material is further subjected to achemisorption step. For example, a compound or material can bechemisorbed to the metal. For example, a sulfur compound such as a thiolor disulfide can be chemisorbed to a second metal such as gold. Forexample, one or more biomolecules including receptors, ligands,antibodies, antigens, polypeptides or polynucleotides can be chemisorbedto the nanoporous material, directly or indirectly. Intermediate layerscan be used between the metal and the biomolecule of interest. Theresulting nanoporous material can be used for various biologicalapplications including, for example, cell culture, drug delivery, anddetecting one or more analytes from a sample via, for example,antigen-antibody interaction, receptor-ligand interaction, or DNA-DNAinteraction.

In one embodiment, the nanoporous material is further chemicallymodified. For example, the material can be modified with a lumiphore forthe detection of analytes through absorption changes in the opticalproperties upon binding.

In one embodiment, the nanoporous material is further used in a metalplasmon frequency monitoring process.

Metastable Alloy Embodiment

Metastable alloys can be prepared. Non-thermodynamic pathways to newmorphology can be prepared. In other words, metastable phases can beformed. An example is a quasicrystal with five-fold symmetry forhydrogen storage.

Applications

Additional applications can be found for both the treated structures aswell as treated structures subjected to a removal or de-alloying step.

One application for embodiments described herein includes opticsfabrication. Examples of such applications include transparentconductors or waveguides.

One application for embodiments described herein includes electronicsfabrication. Examples of such applications include organic electronicdevices, including organic photovoltaic devices and electroluminescentdevices, electrodes, and interconnects.

One application for embodiments described herein includes heterogeneouscatalysis. Examples of such applications include hydrogenation andoxidation.

Another application for embodiments described herein includes bioanalytedetection. Examples of such applications include SERS.

Another application for embodiments described herein includes as astructural material.

Another application for embodiments described herein includes materialswith desirable transport properties. Examples include electrodes.

Another application for embodiments described herein includes as ITOreplacement. The material can be conductive and transparent.

Another application for embodiments described herein includes in fuelcells including gas diffusion membranes.

Another application for embodiments described herein includes asmagnetic material. In one examples, the magnetic material is a metallicalloy comprising nickel.

In another application for embodiments described herein, the porousmaterial can be used as a framework for other materials.

In another application for embodiments described herein, the porousmetal material, attached with biomolecules, can be used for detectingone or more analytes from a sample.

In another application for embodiments described herein, the porousmetal material, due to its unique electrical property, can be used forstimulating muscle responses in vivo.

In another application for embodiments described herein, the porous goldmaterial can be used as a sensor including, for example, glucosesensors.

Devices can be prepared comprising the materials prepared by methodsdescribed herein.

Additional Selected Preferred Embodiments

In one embodiment, the first and second metals are silver, gold, copper,or platinum, and the precursor composition further comprises at leastone solvent.

In one embodiment, the first and second metals are silver or gold, andthe precursor composition further comprises at least one hydrocarbonsolvent.

In one embodiment, the first and second metals are silver or gold, andthe precursor composition further comprises at least one solvent, thedepositing step comprises ink jet printing, and the treating step is aheating step at a temperature of less than 250° C., and the optionalremoving step is carried out by chemical etching.

WORKING EXAMPLES

Instrumentation and Methods: SEM/EDX analysis was performed on a PhilipsXL-30 SEM. Powder X-ray diffraction analysis was performed using aRigaku PXRD machine. Inkjet printing was carried out on a Dimatixprinter. NMR was used to confirm structures in some examples. Spincoating was carried out with use of a SCS G3P-8 spin coater. Dropcasting was carried out with use of a pipette on glass or silicon.

Sources of materials included Aldrich, Amresco, Fisher, STREM, and VWR.

Purification of Materials: Materials were filtered and volatiles removedunder vacuum in some examples. Solvents were distilled over calciumhydride in some examples.

Example 1. Silver Component: (N-Propylethylenediamine SilverIsobutyrate)

0.67 g (3.4 mmol) of silver isobutyrate (prepared as described in U.S.Ser. No. 12/941,932) was massed and set to stir under N₂. To this wasadded 4.2 ml (34 mmol) of N-propylethylenediamine via a glass syringe.After 10 minutes under nitrogen at room temperature, all solidsdissolved to afford a clear, homogeneous solution. After 2 h, the excessN-propylethylenediamine was removed in vacuo leaving behind a yellow,deliquescent waxy solid. A 100 mg/ mL toluene solution was made andfiltered through a 0.45 μm syringe filter yielding the ink product.

Example 2. Gold Component (Tetrahydrothiophene Gold Isobutyrate)

1.88 g (5.87 mmol) of tetrahydrothiophene gold chloride (prepared asdescribed in U.S. Ser. No. 12/941,932) was added to 1.37 g (7.03 mmol)silver isobutyrate (prepared as above) and stirred in 30 mL tolueneforming a white suspension. This mixture was stirred overnight underambient conditions (air at room temperature) yielding a heterogeneousyellow solution with gray solids. The solids were removed by 0.45 μmsyringe filter and the volatiles removed in vacuo yielding a viscousbrown oil. The ink was made by diluting this oil to a 100 mg/mL toluenesolution which was again syringe filtered.

The reaction is illustrated below:

Example 3. Precursor Composition

After filtration, silver and gold inks were mixed at room temperature ina volume ratio equivalent to the desired final film metal stoichiometry.The resulting composition was a homogeneous mixture as determined byvisualization with the unaided eye. Spin coating was carried out withEDX of spun films.

Example 4. Metal Alloy Films

Films made from a 50:50 gold:silver ink (atomic ratio) were spun cast onphosphorus doped silicon which had been washed with hexane/acetone/IPAand ozone treated. Films were spun at 800, 1500, and 5,000 rpm andheated to 250° C. for 20 min.

Example 5. Etching

A 800 rpm and a 5,000 rpm film, as prepared in example 4, were eachsubmerged in 3M HNO₃ overnight and sonicated for 10 min. Films showedincreased optical transparency post etch and were susceptible todelamination.

Example 6. Analysis of Films Before Etching

FIG. 1 illustrates one embodiment, showing varying gold:silver ratiosafter ink metallization.

FIG. 2 illustrates one embodiment, showing SEX/EDX of 60% Ag and 40% Au(atomic ratio) inkjet printed alloy line (lower magnification). Spectrumprocessing: No peaks omitted. Processing option: All elements analyzed(Normalised). Number of iterations=2.

Element Weight % Atomic % Ag L 46.31 61.17 Au M 53.69 38.83 Totals100.00

FIG. 3 illustrates one embodiment, showing SEM/EDX of 60% Ag and 40% Au(atomic ratio) inkjet printed alloy line (higher magnification comparedto FIG. 2). Spectrum processing: No peaks omitted. Processing option:All elements analyzed (Normalised). Number of iterations=2.

Element Weight % Atomic % Ag L 45.40 60.29 Au M 54.60 39.71 Totals100.00

FIG. 4 illustrates one embodiment, showing SEM/EDX of 20% Ag and 80% Au(atomic ratio) inkjet printed alloy line. Spectrum processing: No peaksomitted. Processing option: All elements analyzed (Normalised). Numberof iterations=2.

Element Weight % Atomic % Ag L 12.37 20.50 Au M 87.63 79.51 Totals100.00

FIGS. 5A, 5B, and 5C illustrate one embodiment, showing structuralcharacterization by PXRD of the resulting metallic alloy films from anink containing a 50% Ag and 50% Au atomic ratio (5C), as well as theindividual metals Ag (5A) and gold (5B). Silver and gold crystallize inface centered cubic (FCC) and have nearly identical lattice constants,thus the diffraction patterns of these metals support the formation ofsilver and gold crystalline films.

FIGS. 6A and 6B illustrate one embodiment, showing diffraction overlaysof Au, Ag and the resulting alloy films from an ink containing a 50% Agand 50% Au atomic ratio. The overlay plots show shifts of the alloypeaks to areas between the silver and gold peaks. The fact that thealloy shows a single peak, as well as its slightly shifted position, isindicative of a solid solution chemical alloy with the Ag and Au atomspositioned randomly about the FCC lattice. FIG. 6A shows a broader rangeof peaks compared to FIG. 6B. The higher angle in FIG. 6B providesbetter resolution. The gold trace is red; the silver trace is blue, andthe alloy trace is green.

Example 7. Analysis of Films After Etching

After etching, the films were inspected including determination if anydelamination from the substrate occurred.

What is claimed is:
 1. A composition comprising: a first metal complexcomprising a first metal having a first ligand and a second ligand,wherein the first ligand is an amine ligand or a sulfur-containingligand and the second ligand is a carboxylate ligand; a second metalcomplex comprising a second metal having a first ligand and a secondligand, wherein the first ligand is an amine ligand or asulfur-containing ligand and the second ligand is a carboxylate ligand,and wherein the second metal complex is different from the first metalcomplex; and at least one solvent, wherein (i) the selection of theamount of the first metal complex and the amount of the second metalcomplex, (ii) the selection of the first ligands and the selection ofthe second ligands for the first and second metals, and (iii) theselection of the solvent are adapted to provide a homogeneouscomposition.
 2. The composition of claim 1, wherein the first metalcomplex is platinum complex, and wherein the second metal complex is agold complex.
 3. The composition of claim 1, wherein the first metalcomplex is gold complex, and wherein the second metal complex is acopper complex.
 4. The composition of claim 1, wherein the first metalcomplex is nickel complex, and wherein the second metal complex is acopper complex.
 5. The composition of claim 1, wherein the second ligandfor the second metal is different from the first ligand for the secondmetal.
 6. The composition of claim 1, wherein the carboxylate ligand ofthe first and second metal complexes is an alkyl carboxylate, whereinthe alkyl group has five or less carbon atoms.
 7. The composition ofclaim 1, wherein the atomic percent of the first metal is about 10% toabout 90% and the atomic percent of the second metal is about 10% toabout 90% relative to the total metal content.
 8. The composition ofclaim 1, wherein the solvent is a polar protic solvent.
 9. Thecomposition of claim 1, wherein the first and second metal complexeseach comprise at least 25 wt. % metal.
 10. The composition of claim 1,wherein the first and second metal complexes each comprise at least 50wt. % metal.
 11. The composition of claim 1, further comprising: a thirdmetal complex different from the first and second metal complexes andcomprising a third metal different from the first and second metals. 12.The composition of claim 1, wherein the precursor composition has aviscosity of less than about 20 cps.
 13. The composition of claim 1,wherein the precursor composition has a viscosity of less than about1,000 cps.
 14. The composition of claim 1, wherein the precursorcomposition has a viscosity of at least about 1,000 cps.
 15. Thecomposition of claim 1, wherein the composition comprises metallicnanoparticles at a level of less than 0.1 wt. %.
 16. The composition ofclaim 1, wherein the composition is totally free of metallicnanoparticles.
 17. A method comprising: depositing at least oneprecursor composition on at least one substrate to form at least onedeposited structure, wherein the precursor composition comprises thecomposition of claim 1; and treating the deposited structure so that thefirst metal and the second metal form elemental forms of the first metaland the second metal in a treated structure.
 18. The method of claim 17,wherein the depositing step comprises spin coating, slot-die deposition,spraying, screen printing, ink jet printing, gravure, micro-contactprinting, or flexographic printing.
 19. The method of claim 17, whereinthe treating step is a heating step or an exposure to radiation step.20. The method of claim 17, further comprising: removing at least someof the first metal from the treated structure to leave a nanoporousmaterial comprising at least the second metal.